Occlusal wear evaluation apparatus and occlusal wear evaluation method

ABSTRACT

An occlusal wear evaluation apparatus capable of evaluating quantitatively an occlusal wear of a used denture reads three dimensional data of a denture before use and three dimensional data of the denture after use, calculates a difference in a set value of an articulator allowing the maxillary dental arch and the mandibular dental arch of the denture to occlude between the denture before use and the denture after use, by way of simulating movements of a jaw in the articulator with the three dimensional data of the denture before use and the three dimensional data of the denture after use, and indicates the calculated difference.

TECHNICAL FIELD

The present invention relates to an occlusal wear evaluation apparatusand an occlusal wear evaluation method.

BACKGROUND ART

Generally, a denture should be re-configured periodically. Because, acondition in an oral cavity and a muscle force of a patient change overtime, an optimum denture for the patient can not be made by onlyreconstructing a shape before occlusal wear (abrasion due to dentalocclusion) of a presently used denture. Therefore, a dental technicianobserves a condition of the occlusal wear of the used denture to imagean optimum shape of a denture for the patient so as to determinedetailed configuration of a denture to be newly made. For instance, in acase of that the used denture has been unevenly worn, a cusp is adjustedin its shape and position so that a particularly worn part will be hardto be worn and the other part will be easy to be worn.

When making a denture in such way, a detailed configuration of thedenture is determined in a seat of the pants approach by a doctor or adental technician. Therefore, an apparatus that can evaluatequantitatively an occlusal wear of a used denture is desired in order toallow even a less-experienced doctor or dental technician to determinean optimum denture configuration for a patient.

With respect to a denture configuration, JP 2005-329055 A describes asystem scanning three dimensional shape of teeth and indicating theshape of the teeth on a computer, and JP 2004-195152 A describesreplicating or simulating an occlusal condition on a computer usingthree dimensional data of maxillary tooth and mandibular tooth. And, JP2007-111519 A describes a system that indicates teeth in a predeterminedview and at a predetermined magnification on a screen.

SUMMERY OF THE INVENTION

The objects of the present invention is to provided an occlusal wearevaluation apparatus and an occlusal wear evaluation method that canevaluate quantitatively an occlusal wear of a used denture.

In order to achieve the above object, according to the presentinvention, it is provided a first aspect of an occlusal wear evaluationapparatus comprising an input device, an arithmetic device and a displaydevice, wherein the input device is configured to input threedimensional data of a denture before use and three dimensional data ofthe denture after use into the arithmetic device, the arithmetic deviceis configured to calculate a set value of an articulator allowing themaxillary dental arch and the mandibular dental arch of the denture toocclude for each of the denture before use and the denture after use byway of simulating movements of a jaw in the articulator with the threedimensional data of the denture before use and the three dimensionaldata of the denture after use, to calculate a difference in the setvalue between the denture before use and the denture after use, the setvalue including at least one of a distance between condyle paths, adistance between a maxillary dental arch and a mandibular dental arch,an inclination of a sagittal condylar path, an angle of a balancing sidelateral condylar path, an amount of an immediate side shift, an angle ofa working side lateral condylar path, an inclination of sagittal incisalpath, and a guidance angle of a lateral incisal path, and the displaydevice is configured to indicate the difference in the set valuecalculated by the arithmetic device.

And, according to the present invention, it is provided a second aspectof an occlusal wear evaluation apparatus comprising an input device, anarithmetic device and a display device, wherein the input device isconfigured to input three dimensional data of a plurality of denturesused by a same patient into the arithmetic device, the arithmetic deviceis configured to calculate a set value of an articulator allowing themaxillary dental arch and the mandibular dental arch of the denture toocclude for the each denture, by way of simulating movements of a jaw inthe articulator with the three dimensional data of the dentures, the setvalue including at least one of a distance between condyle paths, adistance between maxillary dental arch and a mandibular dental arch, aninclination of a sagittal condylar path, an angle of a balancing sidelateral condylar path, an amount of an immediate side shift, an angle ofa working side lateral condylar path, an inclination of a sagittalincisal path and a guidance angle of a lateral incisal path, and thedisplay device is configured to indicate the set values calculated bythe arithmetic device in a time series chart.

In a denture, because a portion where is heavily used tends to begreatly worn, a lot of jaws inclines when an occlusion due to an unevenwear. Therefore, in the occlusal wear evaluation apparatus according tothe present invention, if a relative angle between the maxillary dentalarch and the mandibular dental arch of the denture in a centric occlusalposition is calculated, an unevenness of the wear can be quantitativelyrecognized. Accordingly, a countermeasure such as to reduce unevennessof wear by increasing a contacting area in a mostly used portion can betaken.

And, in the occlusal wear evaluation apparatus according to the presentinvention, if a relative position between the maxillary dental arch andthe mandibular dental arch of the denture in a centric occlusal positionis calculated, variance of an occluding position can be obtained.

And, in the occlusal wear evaluation apparatus according to the presentinvention, if at least one of a relative moving distance and a relativemoving angle of a sliding movement between the maxillary teeth and themandibular teeth of the denture from a first occlusal condition to asecond occlusal condition is calculated, a variance in a slidingmovement of the teeth can be determined.

And, in the occlusal wear evaluation apparatus according to the presentinvention, if a volume of the denture is calculated, a total worn amountcan be recognized.

And, in the occlusal wear evaluation apparatus according to the presentinvention, a height of a cusp which is often used as a reference pointmay be calculated.

And, in the occlusal wear evaluation apparatus according to the presentinvention, difference of angles of planes which represent a certain areaof the denture may be calculated.

Further, a first aspect of an occlusal wear evaluation method accordingto the present invention comprises inputing three dimensional data of adenture before use and three dimensional data of the denture after useinto a computer, calculating a difference between the denture before useand the denture after use in a set value of an articulator allowing themaxillary dental arch and the mandibular dental arch of the denture toocclude, by way of simulating movements of a jaw in the articulator withthe three dimensional data of the denture before use and the threedimensional data of the denture after use on the computer, the set valueincluding at least one of a distance between condyle paths, a distancebetween maxillary dental arch and a mandibular dental arch, aninclination of a sagittal condylar path, an angle of a balancing sidelateral condylar path, an amount of an immediate side shift, an angle ofa working side lateral condylar path, an inclination of a sagittalincisal path and a guidance angle of a lateral incisal path which areset values, and indicating the calculated deference on a screen.

Further, a second aspect of an occlusal wear evaluation method accordingto the present invention comprises inputing three dimensional data of aplurality of denture used by a same patient into a computer, calculatinga set value of an articulator allowing the maxillary dental arch and themandibular dental arch of the denture to occlude for the each denture byway of simulating movements of a jaw in the articulator with the threedimensional data of the dentures on the computer, the set valueincluding at least one of a distance between condyle paths, a distancebetween maxillary dental arch and a mandibular dental arch, aninclination of a sagittal condylar path, an angle of a balancing sidelateral condylar path, an amount of an immediate side shift, an angle ofa working side lateral condylar path, an inclination of a sagittalincisal path and a guidance angle of a lateral incisal path, andindicating the calculated set values in a time series chart on a screen.

According to the present invention, a wear of a denture due to use. isquantified to be indicated, and therefore a correct diagnosis and are-design of a denture can be made.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of an occlusal wearevaluation apparatus as an embodiment of the present invention;

FIG. 2 is an example of a screen indication of the occlusal wearevaluation apparatus in FIG. 1;

FIG. 3 is a schematic view of a denture before use evaluated on theocclusal wear evaluation apparatus in FIG. 1;

FIG. 4 is a schematic view of a denture after use evaluated on theocclusal wear evaluation apparatus in FIG. 1;

FIG. 5 is an example of a chart indicated on the occlusal wearevaluation apparatus in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, an embodiment of the present invention is described withreferring drawings. An occlusal wear evaluation apparatus according tothe present invention can be realized using a computer system thatcomprises an arithmetic device 1, a data input device 2, a displaydevice 3 and a user input device 4 as shown in FIG. 1.

The arithmetic device 1 can be substantialized using a personal computerand a software program, while the arithmetic device 1 may be exclusivelydesigned. The data input device 2 can be not only an apparatus such asthree dimensional scanner reading directory three dimensional shape, butalso a device for inputting three dimensional data which is read by anexternal three dimensional scanner and the like into the arithmeticdevice 1, such as a media reading device, for instance a memory deviceor a disc drive, or a data communication device. The display device 3may be a common display. As the user input device 4, a generalized inputdevice such as a keyboard and a mouse can be used.

The occlusal wear evaluation apparatus according to the presentinvention uses the data input device 2 to input three dimensional dataof a denture before use and three dimensional data of the same denturewhich has been used by a patient and worn, into the arithmetic device 1,and calculates variations in various physical quantities of the denturebetween before and after use so as to indicate on the display device 3.

FIG. 2 shows an example of a screen indication of the display device 3.In this example, a sectional display portion 5 for indicating asectional view of the denture is arranged in an upper left part of thescreen, a result display portion 6 for indicating differences inphysical quantities of the denture before and after use is arranged in alower left part of the screen, and a general display portion 7 forindicating the entire denture schematically and specifying a position ofa cross-section indicated in the sectional display portion 5 is arrangedin right part of the screen.

The sectional display portion 5 indicates a sectional shape of thedenture after use and a sectional shape of the same denture before useat the same position in an overlaid manner with different line typesand/or colors. As an example, in FIG. 2, a sectional shape of a dentureafter use is indicated by solid lines, and an outline of a cross-sectionof the same denture before use sectioned at the same position isindicated by dashed lines. Thereby, a wear of the denture in a certaincross-section is visualized in an understandable manner.

The result display portion 6 indicates a difference in physicalquantities between a denture before use and the denture after use(variations due to an occlusal wear). The differences in physicalquantities calculated by the arithmetic device 1 and indicated in theresult display portion 6 include a variation in a relative angle betweena maxillary dental arch and a mandibular dental arch, a variation in arelative position between a specific reference point of a maxillarydental arch and a specific reference point of a mandibular dental arch(such as an occlusal vertical dimension).

The physical quantities indicated in the result display portion 6include a relative moving distance and a relative moving angle in asliding movement between a maxillary teeth and a mandibular teeth from afirst occlusal condition (for instance, a centric occlusal position) toa second occlusal condition (for instance, a lateral occlusal position),a volume of a denture and a height of a cusp. The differences inphysical quantities indicated in the result display portion 6 mayfurther include an angular difference (a variation in a direction of anormal line) of planes which represent a certain area of the denture,for instance, planes approximated by the method of least-square, and thelike.

Further, the variations indicated in the result display portion 6 mayinclude differences between before and after use in physical quantities(for instance, sectional area and height) in the cross-section indicatedon the sectional display portion 5.

Further, the occlusal wear evaluation apparatus preferably simulatesmovements of a jaw in an articulator by the arithmetic device 1 so thatvariations in set values (for instance, a distance between condylepaths, a distance between maxillary dental arch and a mandibular dentalarch, an inclination of a sagittal condylar path, an angle of abalancing side lateral condylar path, an amount of an immediate sideshift, an angle of a working side lateral condylar path, an inclinationof a sagittal incisal path and a guidance angle of a lateral incisalpath) in the articulator can be calculated to be indicated on the resultdisplay portion 6.

The general display portion 7 is mainly intended to be utilized by auser to determine a cross-sectional position to be indicated on thesectional display portion 5, thorough the user input device 4.Therefore, the general display portion 7 is to show dental archesschematically, and not required to show any specific shape based on anactual data. The display on the sectional display portion preferably issuccessively renewed together with a relocation of the cross-sectionalposition determined in the general display portion 7. While it is alsoidealistic that the indication in the result display portion 6 issuccessively renewed together with a relocation of the cross-sectionalposition, the indication in the result display portion 6 may be renewedat a timing designated by a user via the user input device 4, so as toreduce an arithmetic load for the arithmetic device 1.

The general display portion 7 indicates bar handles for moving cursorson the screen using the user input device 4 so as to move and rotate thedisplayed dental arches in respective directions of x, y, z, bar handlesto designate a cross-sectional position to be displayed in the sectionaldisplay portion 5 on the dental arches displayed in the general displayportion 7, and a bar handle for zooming the display in the sectionaldisplay portion 5.

Further, the general display portion 7 preferably specifies a positionin which a difference of a physical quantity as indicated in the resultdisplay portion 6 is maximized and is able to indicate the position onthe screen. For instance, a position of a cusp which has most greatlyvaried in position, a tooth which has most greatly changed in volume andothers may be specified in a manner of changing color, indicating amarker or the like.

FIG. 3 schematically shows a denture before use and FIG. 4 schematicallyshows the denture after use, in order to describe how to utilize theocclusal wear evaluation apparatus according to the present invention.The occlusal wear evaluation apparatus occludes the three dimensionaldata of the maxillary teeth and three dimensional data of the mandibularteeth respectively for the denture before use and the denture after useso as to replicate respective centric occlusal positions wherecontacting points are maximized. Then, difference between a relativeangle of the mandibular dental arch with respect to the maxillary dentalarch of the denture before use and a relative angle of the mandibulardental arch with respect to the maxillary dental arch of the dentureafter use is calculated, as three angles in axial directions of x, y, z,to be indicated in the result display portion 6. For instance, x is adirection connecting both condyles, y is a direction perpendicular tothe x axis and parallel to the occlusal plane, and z is a directionperpendicular to x and y.

Further, the occlusal wear evaluation apparatus according to the presentinvention calculates relative positions of the mandibular dental archwith respect to the maxillary dental arch between the denture before useand the denture after use as in a three distances in axial directions ofx, y, z, and indicates the distances in the result display portion 6.This change in relative positions preferably is calculated in a mannerassuming that three points as center points of both condyle paths and acenter point between both cutting edges of central incisors arereference points.

To this end, the occlusal wear evaluation apparatus specifies positionsof articular fossae with respect to the maxillary teeth and positions ofcondyles with respect to the mandibular teeth for the three dimensionaldata of the denture before use. In this case, the articular fossae andthe condyles in the denture before use are determined so that thearticular fossae and the condyles respectively coincide with each otherin the centric occlusal position. For the denture after use, positionsof articular fossae and positions of condyles are calculated withassuming that the relative position between the maxillary teeth and thearticular fossae and relative position between condyles and themandibular teeth specified for the denture before use do not change.

Notably, the positions of the reference points on the maxillary teethand the positions of the reference points on the mandibular teethcoincide in FIG. 3, and therefore relative positions between thereference points on the maxillary teeth and the reference points areequal to the variations between the FIG. 3 and FIG. 4.

A denture in which relative angle between the maxilla and the mandibledoes not vary due to an occlusal wear is considered as being in an idealcondition where abrasions are even without an uneven wear. And, a changein a position of the condyle of the denture with respect to thearticular fossa due to an occlusal wear is considered as suggesting apossibility of a temporomandibular arthrosis. Therefore, these figuresgive great indications to evaluate whether or not the denture is adaptedto the patient.

Also, a change in height of cusp of each tooth gives an indication tomake a diagnosis of an occlusion. Specifically, variations of heights ofa buccal cusp of mandibular first molar and a mesiolingual cusp ofmaxillary first molar give indications of variation in an occlusalvertical dimension.

Further, the occlusal wear evaluation apparatus can determine andindicate a portion with a large variation between before and after use,i.e. a largely worn portion, so as to notify a doctor or a technician ofa position to be especially attended.

Further, in a case where a volume of the denture is significantlyreduced, a crunching (unintentional biting) is suspected.

Further, the occlusal wear evaluation apparatus according to the presentinvention preferably can indicate differences in a physical quantitybetween before and after use in comparison among plural dentures. FIG. 5shows a chart of variations in a relative angle between maxillary dentalarches and mandibular dental arches due to wear of the respectivedentures which are remade for a same patient every half year. In thisexample, the variation in the relative angle gets smaller gradually, andtherefore it can be confirmed that newer denture is better adapted tothe patient.

A variation in a relative angle between a maxillary dental arch and amandibular dental arch due to: occlusal wear can be caused by analteration of a configuration of a denture as well as by a variation inmasticatory ability due to change in muscle strength or other reasons.Therefore, this information does not lead an absolute conclusiondirectly, but is beneficial information contributory to make anintegrated diagnosis by a doctor with an interview result and the likein mind.

REFERENCE SIGN LIST

-   1 arithmetic device-   2 data input device-   3 display device-   4 user input device-   5 general display portion-   6 result display portion-   7 sectional display portion

1. An occlusal wear evaluation apparatus comprising an input device, anarithmetic device and a display device, wherein the input device isconfigured to input three dimensional data of a denture before use andthree dimensional data of the denture after use into the arithmeticdevice, the arithmetic device is configured to calculate a set value ofan articulator allowing the maxillary dental arch and the mandibulardental arch of the denture to occlude for each of the denture before useand the denture after use by way of simulating movements of a jaw in thearticulator with the three dimensional data of the denture before useand the three dimensional data of the denture after use, to calculate adifference in the set value between the denture before use and thedenture after use, the set value including at least one of a distancebetween condyle paths, a distance between a maxillary dental arch and amandibular dental arch, an inclination of a sagittal condylar path, anangle of a balancing side lateral condylar path, an amount of animmediate side shift, an angle of a working side lateral condylar path,an inclination of sagittal incisal path, and a guidance angle of alateral incisal path, and the display device is configured to indicatethe difference in the set value calculated by the arithmetic device. 2.The occlusal wear evaluation apparatus according to claim 1, wherein thearithmetic device is configured to calculate a relative angle betweenthe maxillary dental arch and the mandibular dental arch of the denturein a centric occlusal position, and the display device is configured toindicate the relative angle calculated by the arithmetic device.
 3. Theocclusal wear evaluation apparatus according to claim 1, wherein thearithmetic device is configured to calculate a relative position betweenthe maxillary dental arch and the mandibular dental arch of the denturein a centric occlusal position, and the display device is configured toindicate the relative position calculated by the arithmetic device. 4.The occlusal wear evaluation apparatus according to claim 1, wherein thearithmetic device is configured to calculate at least one of a relativemoving distance and a relative moving angle of a sliding movement of themaxillary teeth and the mandibular teeth of the denture from a firstocclusal condition to a second occlusal condition, and the displaydevice is configured to indicate at least one of the relative movingdistance and the relative moving angle calculated by the arithmeticdevice.
 5. The occlusal wear evaluation apparatus according to claim 1,wherein the arithmetic device is configured to calculate a volume of thedenture, and the display device is configured to indicate the volumecalculated by the arithmetic device.
 6. The occlusal wear evaluationapparatus according to claim 1, wherein the arithmetic device is furtherconfigured to calculate a height of a cusp of the denture, and thedisplay device is configured to indicate the height of the cuspcalculated by the arithmetic device.
 7. The occlusal wear evaluationapparatus according to claim 1, wherein the arithmetic device is furtherconfigured to calculate an angular difference of planes which representa certain area of the denture, and the display device is configured toindicate the angular difference calculated by the arithmetic device. 8.An occlusal wear evaluation apparatus comprising an input device, anarithmetic device and a display device, wherein the input device isconfigured to input three dimensional data of a plurality of denturesused by a same patient into the arithmetic device, the arithmetic deviceis configured to calculate a set value of an articulator allowing themaxillary dental arch and the mandibular dental arch of the denture toocclude for the each denture, by way of simulating movements of a jaw inthe articulator with the three dimensional data of the dentures, the setvalue including at least one of a distance between condyle paths, adistance between maxillary dental arch and a mandibular dental arch, aninclination of a sagittal condylar path, an angle of a balancing sidelateral condylar path, an amount of an immediate side shift, an angle ofa working side lateral condylar path, an inclination of a sagittalincisal path and a guidance angle of a lateral incisal path, and thedisplay device is configured to indicate the set values calculated bythe arithmetic device in a time series chart.
 9. The occlusal wearevaluation apparatus according to claim 1, wherein the arithmetic deviceis configured to calculate a relative angle between the maxillary dentalarch and the mandibular dental arch of the denture in a centric occlusalposition, and the display device is configured to indicate the relativeangle calculated by the arithmetic device.
 10. The occlusal wearevaluation apparatus according to claim 8, wherein the arithmetic deviceis configured to calculate a relative position between the maxillarydental arch and the mandibular dental arch of the denture in a centricocclusal position, and the display device is configured to indicate therelative position calculated by the arithmetic device.
 11. The occlusalwear evaluation apparatus according to claim 8, wherein the arithmeticdevice is configured to calculate at least one of a relative movingdistance and a relative moving angle of a sliding movement of themaxillary teeth and the mandibular teeth of the denture from a firstocclusal condition to a second occlusal condition, and the displaydevice is configured to indicate at least one of the relative movingdistance and the relative moving angle calculated by the arithmeticdevice.
 12. The occlusal wear evaluation apparatus according to claim 8,wherein the arithmetic device is configured to calculate a volume of thedenture, and the display device is configured to indicate the volumecalculated by the arithmetic device.
 13. The occlusal wear evaluationapparatus according to claim 8, wherein the arithmetic device is furtherconfigured to calculate a height of a cusp of the denture, and thedisplay device is configured to indicate the height of the cuspcalculated by the arithmetic device.
 14. The occlusal wear evaluationapparatus according to claim 8, wherein the arithmetic device is furtherconfigured to calculate an angular difference of planes which representa certain area of the denture, and the display device is configured toindicate the angular difference calculated by the arithmetic device. 15.An occlusal wear evaluation method comprising inputing three dimensionaldata of a denture before use and three dimensional data of the dentureafter use into a computer, calculating a set value of an articulatorallowing a maxillary dental arch and a mandibular dental arch of thedenture to occlude for each of the denture before use and the dentureafter use by way of simulating movements of a jaw in the articulatorwith the three dimensional data of the denture before use and the threedimensional data of the denture after use on the computer, to calculatea difference in the set value between the denture before use and thedenture after use, the set value including at least one of a distancebetween condyle paths, a distance between a maxillary dental arch and amandibular dental arch, an inclination of a sagittal condylar path, anangle of a balancing side lateral condylar path, an amount of animmediate side shift, an angle of a working side lateral condylar path,an inclination of sagittal incisal path, and a guidance angle of alateral incisal path, and indicating the calculated deference on ascreen.
 16. An occlusal wear evaluation method comprising inputing threedimensional data of a plurality of denture used by a same patient into acomputer, calculating a set value of an articulator allowing themaxillary dental arch and the mandibular dental arch of the denture toocclude for the each denture by way of simulating movements of a jaw inthe articulator with the three dimensional data of the dentures on thecomputer, the set value including at least one of a distance betweencondyle paths, a distance between maxillary dental arch and a mandibulardental arch, an inclination of a sagittal condylar path, an angle of abalancing side lateral condylar path, an amount of an immediate sideshift, an angle of a working side lateral condylar path, an inclinationof a sagittal incisal path and a guidance angle of a lateral incisalpath, and indicating the calculated set values in a time series chart ona screen.